Communication system



Apr1l 12, 1927. w. UNEILL- COMMUNICATION SYSTEM Filed Dec. 17, 1924 5Sheet-She'et 1 lnrenfvn' Y Henry If. 0772/7! by Alf}! April 1927' H. w.O'NEILL COMMUNIGATION SYSTEM Filed Dec. 17, 1924 5 Sheets-Sheet 2/nrehfor: flew/y I1. 4772/ 1927. April 12 H. w. O'NEILL cpmuNIcA'rIouSYSTEM M 3 I W. m RQ m 5 V in h 4 E 1 H H i m M Y 12 1921. 1624 672 n 7w. ONEILL CUMMUNICATION SYSTEM Filed Dec. 17, 1924 Sheets-Sheet 4 wwwMum \NM\ a e w m u M. v u U .R 3 S 3 Filed Dec. 17, 1924 5 Sha ts-Sheet5 .3 NM \Nw 83 m lg x N Mk v a h. Q J 4. M a w x N \\M 4 (x s v 9 m QQQQ N f Y. J, N svs g S M v 7 2w Patented Apr. 12, 1927.

UNITED if srarss HENRY ONEILL, OF ELMI-IURST, NEW YORK, ASSLGNOR TOWESTERN ELECTRIC YEICE...

COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

, COMMUNICATION SYSTEM.

Application filed December 17,1924. Serial No. ass r03.

This invention relatesto communication systems and more particularly tosystems of radio-wire communlcatlon.

The object. of this invention is to provide a system whereby land linesor wire circuits may be joined to radio systems for the optionalhandling of either telephone or telegraph messages. v r

A feature of the invention is the employment of an improved systeminvolving a plurality of switching equipments respectively located atseparate points relative to radio transmitting and, receiving sets andarrangedin such a manner that the establishment and control ofradio-wire connec-' tions may rest either with a single switchingpointor the control may be divided between a plurality of such points, andfurther, that such joint control may be on either of several'difterentplans, as a parallel relation or aseries relation or a combie nation ofparalleland series relations relative toth'e circuits of the switchingfacilities at the different points. a

. Another feature is the provision for reciprocal control of the calland supervisory signals relative to radi circuits or channels.

I Anotherfeature is the pIOVlSlOIl of an arrangement for the wire sideof a connection whereby either two-wire orfour-wire working may.be'resorted to, while equipment.

automatically responsive to the handling of traffic may render receivingand sending devices of an attendants equipment effective with circuitsancillary to and differing from the main channelsof a connection.

Another feature is the provision of an arrangement whereby any switchingpoint may serve either as a terminating station or as a repeater stationrelative to the handlin'g of communications over wire or radio channelsor on mixed connections relative to wire and radio working or onwire-towire communications. 1 Another featureis the provision ofimproved meansv for supplying so-calledside tone relative to transmitterand receiver of a telephone set when these instruments may berespectively associated with electricallyv isolated circuits usuallypresent in four-wire working.

Another feature. is the provision of an improved signaling arrangementwhereby o channels and wire asingle visual signaling deviceis emplovedboth as a calling signal and as a clearingout signal. 7 v P Anotherfeature isthe provision of a circuit arrangement wherein an. incomingline .is provided with a visual signal device at each of twof operatorsboards and means actuated when thecall is answered from one board forretiring both :signals, and

means for reoperating only the signal at the board Where the call isanswered when the calling party disconnects.

Another feature is the provision of an arrangementwhereby the receiver,may be applied to either side of a four-wire circuit for communicationpurposes, the impedance ofthe circuit being increased when the re ceiver1s employed for monitoring purposes Another feature is the provision, ofa circult arrangement involving compensating means inthe operators; setwhich renders the voice currents impressed on the ampli- "fiers theoperator of substantially the same intenslty as those which would beim-\ pressed from the transmitting end, that is, this resistance ineffect, sets the operator back to the transmitting end and makes itunnecessary to adjust the gain device before and after the. operatorcalls.

improved system to prevent false signals Another feature is. theprovision of an Another feature is the provision of a coin from the landlines from operating the calling signals. e

Another, feature is the] provision tea e11- cuit arrangement whereby lowfrequency oscillations are impressed on high frequency oscillations fromeither one of two points connected in. a directmirrent circuit.

Another feature is the provision oftwo alternating current relays in thesignaling circuit tuned to respond to differentfrequencies, preferablywithin the voice range, and a signal operated only on the simultaneousresponse of both relays.

Another feature is the provision of a monitoring setincluding aninduction coil having a high impedance prin'ia-ry winding connectedacross the cord being monitored,

an amplifier being connected to the secondary winding, wherebytransmission is not impaired.

Another feature is the provision of an arrangement whereby the operatormay modulate the carrier waves by voice currents or low frequencytelegraph waves without changing the transmitting circuit, the circuitsbeing so arranged that when the telegraph key is in the operatedposition, the talking transmitting circuit is In operative relation withthe radio trammitter. I

Another feature is the provision of a cir-- cuit for eliminating theringing key in the cord circuit and consists in providing a common relayassociated with the signaling generator, and a relay in each linecircuit, the common relay being actuated upon the operation of thegenerator, and the relay in the line taken for use being operated due tothe conjoint actuation of the common relay and the talking key of thecord used. A related feature is the provision of a circuit arrangementfor applying signaling current to the line over a path independent ofthe cord used and at a point beyond the terminating equipment of saidline, said equipment being of a character opaque to such low frequencysignaling currents.

Another feature is the provision of a circuit arrangement involving theapplication of a substantially zero resistance ground, to the highfrequency currents used in radio transmission, to one of the strands ofthe cord circuits to prevent interference.

Another feature is the provision of a circuit arrangement forcommunicating systems using four-wire circuits, the receiver andtransmitter being connected respectively to the two sides of the circuitfor affording side tone without physically con necting the two sides ofthe four-wire circuit, consisting in providing means for directing aportion of the energy fromthe transmitter to the receiver withoutestablishing a path whereby an appreciable amount of energy istransferred between the two sides of the four-wire circuit.

' Another feature relates to communicating ystems using four-wirecircuits wherein two of the wires are used for transmitting and two forreceiving, consisting in the provision of manually controlled switchesfor utilizing either of said pa'rs for local telephone conversations.

Other features of the invention will appear from the followingdescription together with the appended drawings in which Fig. 1 showsthe terminating equipment T, line L, equipment. OT of and in connec tionwith an operators telephone set, a cord circuit C of the two wire type,Fig.

1 shows line circuits L1 and 11-2 four wire working which may be used inplace of the two wire line L of Fig. 1.

Fig. 2 shows a four wire circuit C1, telephone signaling equipment,telegraph signaling equipment S1, and a system for measuring thestrength of voice and telegraphic currents.

Fig. 3 shows equipment RT of a radio transmitting system with circuitfacilities corresponding to a radio receiving system RR and a trunk andline equipment TL while equipments L-3, T1, OT-1, C2, S2, S3 and M-1 maybe considered, respectively, as corresponding with equipments L, T, OT,C, S, 8-1 and M of Figs. 1 and 2.

Fig. 4 shows the radio equipment for a ship; while Fig. 5 shows theequipment for a second radio station with'the equipments of either Fi s.1, 2 and 3 or other stations having equipment similar to the system ofFig. 1. In describing this system the equipments of Fig. 1 and Fig. 2and that portion of equipment of the radio system to the left of line D(Fig. may be considered present at a radio wire station at which radiotransmitting equipment HT is present while the equipment at the rightside of line D may be considered as located at a radio wire receivingstation- The line circuit L (Fig. 1) may be considered as extending to adistant toll or long distance telephone switchboard and through whichconnections may be estab lished with other land lines. This two wirecircuit terminates in a repeating coil 1 of .the hybrid type having asecondary winding 2 joined to a jack 3 while thebridge points of thecoil 1 are connected to an autotransformer l, which in turn is connectedto a jack 5. The purpose of the auto transformer is to increase theimpedance of the circuit from the bridge points of coil 1 to correspondwith the impedance of the secondary or output winding 2. The artificialline 6 serves as a balancing network for the line L. The relay 10 iscontrolled from a cord circuit as will be presently described, andserves for disconnecting the hybrid coil and for a plying signalingcurrent outward over the line circuit. During such operations, thisrelay also connects a resistance or network 111, corresponding to thenetwork 6 to maintain a balanced condition at the hybrid coil, wherebythe tra: sfor of energy between the radio transmitting system and theradio receiving system is prevented when the line is disconnected fromthe hybrid coil, during a ringing period. t 7

Called signals from the line L are received asfollows. Ringing currentincoming from the line L flows through the relay for 15, which beingenergized, pulls up its armatrue to thereby open the circuit includingthe normally energized relay 16. The armature of relay 16 thereforefalls off] and completes acircuit including grounded battery,the'windi'ng of relay 17 resistance 19 and relay 201 (Fig. 2) which isconnected toground. The relay 17 being energized, actuates the twoarmatures associated with it.

The left hand armature opens thecircuit of 1 arately shown, keys 210-211may be considered as units forming a single key, while units 215-216,220221, 225 226 and 230-231 may be considered as similarly constitutingsingle keys. The units 2102l1 serve as a so-called splitting key fordisco'ne necting the left-hand end of the cord circuit, while units215-216 form a key to disconnectthe right hand end or radio side of thecord circuit. Units 220-221 permit the operators telephone set to beconnected for talking on .a circuit which may be used to establisha'connection between the line and radio equipment. Units 225226 form akey for monitoring and units 230--231 form a key whereby the operatorstransmitter and receiver may be reversed or transposed relative to thetwo sides of the four wire cord circuit. 7

At the splitting key unit 210, the trans,- former 217 may be connectedto a radio rcceivingsyste'm. During the period of a connection this keymay be operated for the purpose of including a'device M2 whichcorresponds with the current indicating systern M wherebyfwhen the radioside of a connection is disconnected, incoming voice orfsignalingcurrent will be indicated in the system M-2. The resistance units ornetworks 212 and 213 will be connected to the respective sides of thefour wire circuits connected to the line L when the key 210-211 isoperated to disconnect the circuits in that direction. The purpose ofthese resistances is to maintain'a balanced condition relative to theterminating equipment T of the line 'L during suchperiods. The jacks 222and 223 are provided to permitthe speech meter M to be connected bytheplug 224 with either side of the four wire connection. Key units 2021(Fig. 1 are also mechanically connected to form a single key which isused'to control the connection of the 1 transmission loss networks '25and 26 with respect to the circuits at a point intermediate between anoperators telephone receiver 23' .andthe transmitters'22 or 31 and there-' from a transmissionstandpoint,

circuit 'L. Therefore, following the establishnient of aconnection witha distant radio station or ship, galn' controls227 and 228' of i.)

the cord circuit C1 may be set by the operator to determine a speechenergi level which will be satisfactory when the connec tion is extendedthrough or linked to the toll operator at the assumed distant point.

In establishing a connection betvveenline and the radio link, plug& 7-and 8' are -nserted in acks 3 and 5 of the toll line L while plugs20Tand-208 are inserted in, jacks 303 and 305 of the equipment of Fig.3. Incoming radiowaves incident upon the antenna 301 will be supplied tothe radio receiving equipment ER in which theywill'be detected toreproduce speech currcnt.s The detected speech currents will traversethe main conductors of the trunk the main-members of jack 303 and plug207, maincondujctors 203 and 204 of the cord circuit, main members ofjack 7 and. plug 3 and the terminating equipment T of thetoll line L.

Speech currents from theline L will traverse the main contact members ofjack 5 and plug 8, main conductors 205 .and 206 of the cord circuit,main contact members of plug 208 and jack 305, thence to the radiotransmitting equipment RT. A. speech modulated radio frequency wave willbe supplied to and radiated from the transmitting antenna302f 5 I Duringthe'period of the connection just described, it may be desirable for theoperator at the radio receiving station to be. able to talk, monitor,signal," etc. This'may be accomplished by associating a four-wire cordcircuit C-2, including equipment simia lar to that of cord circuit C 1,With the radio transmitting and receiving apparatuses. The cord circuitC-2.may be connected either in parallel, in series, or in" seriesmultiple with the cord circuit C1.

For a parallel connection of the receiving operators set OT-l, with thecord circuit C1; the plugs 307 and 309 of the cord circuit C--2 areinserted in the corresponding jacks 306 and 310.

,To provide for four wire working on the land line side of a cordconnection, the plugs 7 and 8 of the cord circuit C1 should be insertedin jacks 13 and 14, Fig. 1, respectively, of the lines L 1 and L'2 whichform a four wir-ecircuit. Equipment corre: sponding with signalreceiving equipment, constituted by relays 15, 16 and 17 and Sig: nal 18of the line L, is provided at RE on equipment similar to the signalingrelay 10 and associated apparatus of line L.

The arrangement of a connection, where by the switching equipment at thefirst or transmitt'ng station maybe in series or tandem with theswitching equipment at the second or receiving station, is accomplishedby inserting the plugs 207 and 208 of cord circuit C-l in jacks 313 and315 of trunk circuits 314 and 318, respectively. At the second stationplugs four-wire cord circuit C-2 are inserted in jacks 316 and 317 ofthe trunk circuits 314 and 318, while the opposite plugs 307 and 309 areinserted in the jacks 310 and 306, respectively, of the trunk circuits304 and 308 associated with the radio receiving and transmittingsystems. 'Under such an assumed connection, the matter of setting thegain control devices rests with either station. At the station to whichsuch operations may be assigned, a key 229 (Fig. 2) may be operated forconnecting the gain control devices 22? and 228 in circuit with the twosides of the four wire cord circuit.

For a connection, which may be referred to as a series multiplecombination, the plug 207 is inserted in jack 313 of the trunk 314 whileplug 208 is inserted in jack 305 of trunk 308. At the other station,plug 320 of the cord circuit C2 is inserted into jack 316 of the trunk314 and plug 307 is inserted into jack 310 of trunk 304. When thisconnection is made, incoming voice currents from line L will traversethe lower side of the cord circuit C1 and the connection of the trunk308 to the radio transmitting antenna 302, while voice currents arrivingover the receiving antenna 301 will traverse the upper conductors of thefour-wire cord circuit C2, trunk 314, thence over the upper side of thecord circuit C1 to the line L. Thus speech currents resulting fromdetecting the incoming radio waves will be trans mitted in tandemthrough the cord circuits C2 and C1 to the toll line L, while currentsfrom this line to the radio transmitting equipment will traverse onlythe circuits of the cord C1. The radio transmitting equipment however,will be accessible to the lower half or side of the cord circuit 02 atthe second station, if desired, by inserting plug 309 into jack 306. ofthe trunk 308 connected to the radio transmitter.

In a converse manner, eq i-iipmcnt may be placed in series with one sideof the cord circuits C1 and G2 at the respective stations, while theradio receiving circuits will be connected directly through the upperside of the cord circuit 01 to the li-neL. Bridged supervision on theincoming radio channel will be carried out during such periods at thesecond station by inserting plug 307 into jack 310 of the trunk 304.

Referring to the equipment of the operthe transmitting 320 and 321 ofthe ators telephone set (OT, Fig. 1) the telephone transmitter 22, whichmay be ofthe so-called switchboard type, will be energized by insertingplug 24 of the telephone receiver 23 into jack 12. This energizingcircuit extends from grounded battery, through the winding ofretardation coil 9, normal contacts of jack 27, transmitter 22, forwardcontacts of jack 1.2 lower normal contacts of relay 28, primary windingof induction coil 29, conductor 30, thence to ground through the normalcontacts of relay 235 (Fig. 2). l

When it is desired to use a breast transmitter 31, in place of theswitchboard transmitter 22, plug 32 of the transmitter 31 may beinserted in jack 27. The separated contacts of jack 2? will thendisconnect transmitter 22 and the energizing circuit for 31 may betraced from grounded battery, through retardation coil 9, lower mainmembers of jack 27 and plug 32, transmitter 31, upper main members ofthis plug and jack, thence to ground through the circuit already tracedby way of the lower normal contacts of relay 28.

The circuit for the operators receiver 23 may be traced from the lowerterminal of the winding 34 of transformer 33', upper normal contacts 0dof relay 28, lower main members of jack 12 and plug 24, receiver 23,upper main members of plug 24 and jack 12, upper normal contacts cab ofrelay 28 to p the upper terminal of winding 34.

A monitoring system, which when employed will inappreciably effectthetransmission relativeto the operators receiver 23, may be obtained byinserting plug 35 into jack 36, plug 37 into jack 38, and plug 39 intojack 41. Current from grounded battery will traverse a circuit over thelower main members of jack 3 6 and plug 35 to filament 43 of a threeelement vacuum tube amplifier 42- to ground over the sleeve. members ofplug 35 and jack 3.6. Grounded battery also applies current through theupper members of 'aclr 36, plug 35 and primary winding of transformer 45to the plate element 44 of the tube 42. The telephone receiver 40 isconnected by way of plug 39 and jack 41 to the secondary or outputwinding of transformer 45. The main members of jack 38 are connected inparallel to the leads of jack 12 which. connect to receiver 23.Therefore, voice currents over the plug 37 will traverse a circuitthrough the primary winding of transformer 46, the secondary winding ofthis transformer is included in the input circuit of tube 42, which includes a grid element 51. When desired, the operators receiver 23. may.be disconnected from jack 12 and connected to jack 41 and used with thetransmitter 31 in th regular handling of telephone connections, in placeof the monitoring receiver 40. Under these conditions, it is immaterialwhether 24 is in jack 12, transmitter 31, as already traced, isindependent of the lower contacts, of jack 12. These contacts merelyserve to complete the circuit for the transmitter 22. v

To connect the'operators receiver 23 and transmitter 31, with therespective sides'at the cord circuit C1, the key formed ,of units 220221is operated. For the receiver, a circuit may be traced from the mainconductor 203 of the cord, the upper normal contacts fig of key 210, theupper forward contacts 97" of key 220, the upper normal con tacts git;of key 230, conductor 236, the upper plug normal contacts fc of key 20,winding as of transformer 33, lower normal contacts (Z [if keyv 20,conductor 237, lower normalcontacts. 6 of key 230., the lower alternatecontacts (Z0. of key 220, the lower normal contacts do of key210 to theoppositemain conductor 204 of the cord circuit. For the transmitter'31,the circuit istraced from the .inain, conductor 205, the upper normalcontacts cf of key 211, the upper forward contacts kg of key 221, the,upper normal contacts ale of key 231, conductor 238, the upper normalcontacts of relay 49, upper nor-- mal contacts dc, of key 21, secondaryWllldf. 'ingof the induction coil 29-, the lower nor- :mal contacts toof key 21 and lower normal contacts of relay 4:9, conductor 239, thelower normal contacts of key 231, the lower alternate contacts 0d ofkey221 and the lower normal contacts a?) vofkey 211 to. the

main conductor 206. With the circuits just traced, thereceiver 23 willbe connectedun bridge on the upper side of the, four-wire cord circuit,while the transmitter 31 will be similarly connected to the lower sideof the four wire cord circuit. 1

In case the splitting key'210211 is op erated at this time, theoperators set will be connected to plugs 207 and 208 andm'ay be used forcommunication-over the radio circuits. If the splitting key is in itsposition to operate units 215216, the radio side will 'be disconnectedand the. operators set will;

sertion of plug, 7 into jack 3 will separate be connected for usewiththe line L. Operation of the key formed of un1ts2O 21 opens obviousconnections which normally short circuit the series resistance units,while the forward contacts of the shunt resistance units are connectedtogether to form a bridge path for the loss networks, which is of theter may now be traced from conductor 203,

upper normal contacts ]L(/ of-key210, the

upper forward contacts gf of key 220, upper since the circuit for thealternate contacts fe of key 231, coiuluctor 238,. and as already/tracedthrough the secthrough the winding 48 of the'transforme'r 33 returningoverconductor 237, the lower alternate contacts ecZ of k'ey 230, thelower alternate contactsed of key 221, and the lower normal contactsZ766 of key 211 to the opposite main conductor 206.

' .The control described above,increases the flexibility of theconnecting circuit, since it permits the transmitter and receiver of anoperators set to be interchanged with respect to the sides of..the cordcircuit C1,

whereby a'single operators setmaybe properly connected to talk, monitoror signal in either directiomwhether the communication takes place fromline to radio or from radio to line. This is a distinct advantage,especially when repeaters are used between the cord circuit and thedistant radio system, or

betweenthe cord circuit'and the four-wire terminating equipment of thetwo-wire line 14" orthe circuits of the four-wire line formed ofcircuitsL1 and L2. When using a connecting circuit of this type it will beobvious that the repeaters render the respective sides of thefour-wire'circuit opaque to currents in one direction;

such aconnecting circuit, the reversing key order to talk in theopposite. direction, it will be necessary to throw the reversing key tothe opposite position. 'z

pon receiving a call signal fromthe line L, as indicated by the lightingof lamp 18 due to the locked position of relay; 17, in-

the normal contacts of this jack-t0 disconnect ground and thereby effectthe release member of the plug 7'with the sleeve mem- In talking fromthe operators set in one direction over ber of the jack,therebypermitting the release ofrelay '17., Following complete insertionof plug 7- into jack 3, a circuit, in.

substitution of the first path, is completed over the sleeve conductorof plug 7, the lower normal contacts of key 220 to ground throughtherwindingof relay 201 (Fig; 2'). I

vThis providesthat during'the period of a connection, an incomingcallsignal 7 locks up relay to supply the relay 17 over the sleeve conductorof the connection and the lower normal contacts of key 220, so as tomaintain the signal lamp 18 lighted. lVhen the talking key 220-221 isoperated in responding to such a signal, separation of the lower normalcontacts of the unit 220 will open the locking circuit of the relay 17,thereby extinguishing signal 18.

To insure that the signal 18 will not be displayed due to inductive orsurge effects in the conductors of line L, a slow release relay 16 isinserted between the alternating current relay and the signal controlre- My 17 Relay 16 is normally energized over an obvious circuit whichcircuit is opened upon the operation of relay 15. Signaling currentincoming over line L must hold relay 15 energized for a sufficientperiod to allow the contacts of relay 16 to assume the fully releasedposition, in order to remove a shortcir'cuit about the winding of relay17 For signaling outward over the line circuit L, the plug 8 is insertedin jack 5 and the talking key 220'221 operated. Key 240 istlren operatedto apply signaling current from a source 241 to operate relay 242 whichhas a high impedance to signaling currents. Relay 242 causes theenergization of relay 243 over an obvious circuit closure of thecontacts of relay 243, connects ground to a circuit which extendsthrough the lower alternate contacts at of unit 221, the upper sleevemember of plug 8, shell of jack 5, and the winding of relay 10 togrounded battery. The upper armature of relay 10 connects ground to theupper main conductor of line L, while the lower armatureconnec'ts thelower main conductor of the line to conductor now connected over thelower alternate contacts ab of key 240 through the source 241 and theupper alternate contacts cf of the key 240 to ground, whereby current issupplied to line L from the source 241.

Where a continually operating source of alternating current, as thesource 241, may not be available, the key 240 may remain in its normalposition, and the hand generator 244 operated. One side of thisgenerator is normally grounded through the upper normal contacts de ofkey 240, while the opposite side of the generator is connected over thelower normal contacts 0?) of this key to the conductor 50. Under theseconditions the relay 242, connected from the conductor 50 to ground,will respond to current from the hand generator and effect the operationof relay 242, which in turn causes relay 243 to operate; whereby groundpotential will be applied over the sleeve of the connection to energizerelay 10, while energy from the hand generator over conductor 50 will beeffective over the lower armature of ringing current to line L. Theoperation of the current indicating system M may be described asfollows. Let it now be assumed that, during the period of the connectionor while in preparation for a connection, the plug 207 of the cord C1 isconnected to the trunk 304 of the radio receiving equipment RR.Insertion of the plug 224 into jack 222 establishes :a circuit which maybe traced from main conductor 203 over the normal contacts hg of key210,

upper main members of the jack 222 and plug 224, the primary winding oftransformer 286, thence over the lower members of plug 224 and jack 222and the lower normal contact-s do of key 210 to the opposite mainconductor 204. The sleeve members of rents will be respectivelyrectified in this tube to set up uni-directional currents through themeter 285. battery 284 is to neutralize residual current effectscommonly referred to as Edison effect currents, and retain the needle ofthe instrument 285 normally at zero or at any other predetermined pointor position on its associated scale. Therefore, with this stabilizingarrangement response of the needle will be due only to such alternatingcurrents as may arrive from the connected circuit. By transferring theplug 224 to the jack 223 similar readings of voice or other signalingcurrents may be made relative to the opposite side of the four-wirecircuits. The current measuring system M is described more in .detail inmy Patent No. 1,404,311 dated January 24, 1922.

During the period of a connection, the operator may monitor by operatingthe monitoring key formed of units 225-226. A circuit for this purposemay be traced from the main conductor 203, upper normal contacts hg ofkey 210, upper forward con tacts f@ of key "225, upper normal contactsgh of key 230, conductor 236, normal upper contacts fe of key former 33,lower normal contacts do of key 20, conductor 237, lower normal contacts0; of key 230, lower normal contacts (Z6 of key 220, lower normalcontacts 07) of key 230, conductor 52, lower normal contacts of relay53, winding 54 of transformer 33, upper normal contacts of relay 53,conductor 55, upper normal contacts M of key 230, lower forward contactsdo of key 225, lower normal contacts do of key 210 to the opposite Thepurposeof the 20, winding 48 of transtelephone set which will now be ina posi-.

tion to monitor on the upper side; ofgthe four-wire cord circuit, whichmay be. assumed as connected to the trunk circuit 304 for the receptionof voice currents transmit-1 ted from the radioequipment to the line L.

When desired, receiver may be employed for monitoring operations overthe circuits .already traced through amplifier 42 tothe output windings34 and56' of the transformer 33. Y w

During the monitoring period the transmitterof the operators set will,be rendered inoperative; Forthis purpose a circuit may be traced fromground through the upper forwardcontactsef of the key 226 to groundedbatterythrough the windingof relay 49. In responding,,this relay opensthe circuit of. the secondary winding ofthe induction coil 29 of theoperators transmitter.

F or monitoring on the opposite side of the four-wire cord circuit, thekey units 22 5226 are continued in theopcrated or monitoring position,while key units 23023l are also operated. The circuit may now be tracedfrom the mainconductor 205 through the upper normal contacts 6; of relay211, the forward upper; contacts do. of key 226, the upper alternatecontacts z'h of key 230, conductor 236, normal contacts fe of key 20,winding 48 oftransformer 33, lower normal contacts do of key20,conductor 237, lower alternate contacts erlof key 230, lowernormalcontactsefi. ofkey 221, lower alternate contacts ab of key 230,conductor 52, lower normal contacts ofrelay 53,'winding 54 oftransformer 33, upper normal contacts of relay 53, conductor 55, upperalternate contacts [cl ,ofkey230, lower forward contacts 6a of-key 226,lower normal contactsab of key 211-to the opposite main conductor 206ofthecord circuit. WVith the-circuits connected as described above, theoperators telephone receiver will be coupled by the transformer 33 formonitoring on the opposite, i. e. lower, side. of the cord circuit;while the circuit of the operators transmitter, although associated withthe upper sidev of this cord circuit, will continue to stand open at theseparated contacts of relay 49, which-continues operated over thecircuit already described.

TVhererepeater equipments are not pres ent intermediate the cord circuitand the line L, transmission currents from the line L, as Well as fromthe radio receiving equipment, will become efiective in the operatorsrecei'verwhenit is connected to the conduc- 'tors 203 and 204- of thecord circuitfor monitoring purposes. These conductors,'

while forming the pathproper for-the currents to the wire side of theconnection, may also be common to thevoice currents from the line L, theproper or-through path for which, however, is by way of the lowerconductors 205 and 206 of the cord circuit to the radio, transmittingequipment.v At

the hybrid coil the voice currents may divide, a portion flOWlIlglntOthe upper side.

of the four-wire circuit which includes conductors 203 and 204 of thecord circuit.

In case repeater equipments are present between the cord and the line L,the upperside of the four wire cord circuit will not.

be common to voice currents incoming from i the line L, due to therepeaters being opaque to currents in that direction. Therefore, inorder to monitor su'ch currents, it'is neces sary to operate thereversing key v230 -231 to transfer the operators'receiver to thelowerside, formed by the conductors 205 and 206 of the cord circuit. In aconverse manner, thevpresence of the repeaters serves to completelyisolate these conductors with respect to transmission currents arriving.from the radio receiving equipment, which currents in the main may beexcluded by a suficiently accurate condition of balance be tween thereal line L and the artificial line 6. lVhen the operators telephone setis. in position for talking over the cord circuit C1, key units 22022l'being in their operated positions :as already described, it is desirablethat currents corresponding with the socalled side tone effects bepresent in the operators receiver by currents produced by the operatorstransmitter. These efiects are produced in the pres-ent system by meansof transformer 33 as will now be described.

In the talking position of the circuits, winding 34 of the transformerwill be connected to receiver 23, while winding 48. will be connectedinbridge on the conductors 203 and 204' of the cord circuit. -A circuitmay now be traced in half tapped relation from grounded battery, throughretardation coil 9, condenser'58, upper'alternate contacts of relay 53,wind ng 54 of transformer 33 and the lower alternate contacts of therelay to ground. I

During the talking period, relay '53 is'energized by current from.grounded battery through the winding of'this relay over lead 59, upperalternate contacts of unit 220 to ground through relay 201, aspreviously traced. Relay 201 is of the marginaltype and does not respondat this time.

v With the CllCLlltSiAZlCBtl above, it will be seen that condenser 58and winding 54 of transformer 33, form a series path connected inparallel with condenser 60. This condenser is connected in: shuntacrossthe pri mary circuit of the operators telephone set. andconstitutes a path traversed by such voice currents as may be set upwhen the transmitter is in use. Therefore, by employing a suitablecapacity value for con denser 58,a predetermined amount of the voicecurrents, to serve as side tone may be set up in transformer 33 and willbe supplied to the receiver 23 over the circuits already traced. Sidetone effects are recognized requirements for proper transmission, as aspeaker may thereby gauge the amplitude or energy of the voice.

On the four-wire circuit, where a relatively perfect balance obtains atthe terminating equipment T of the line L with respect to the artificialline 6, no currents from conductors 205 and 206 will reach conductors203 and 204-. of the cord circuit. In like manner, in case plugs 7 and 8of the cord circuit are employed with the four-wire, circuit formed oflines L1 and L2, voice currents from the operators transmitter, whenconnected to conductors 205 and 206, will not reach the upper side ofthecord circuit formed by conductors 203 and 204. Therefore. thenecessity for providing the side tone feature will be evident.

Cord circuit C 1) may also be employed with the toll line L. Plug 72 maybe inserted in jack 61 and a connection established by plug 73 either toa trunk circuit 325, a line circuit 326 or a tandem circuit 327. Thecord circuit C which is of the twowire type may also be employed inestablishing the connections between the circuits 325 and 327 or betweenother two-wire circuits not shown but present in the system.

In describing the two-wire circuits, it will be understood, as alreadymentioned, that the cord circuit equipment C3 (Fig. 3) may be aduplicate of the cord circuit C. Assuming that a call has originatedover the trunk circuit 325 by the insertion of plug 73 of the cordcircuit G into jack 330 of trunk 325, a circuit may be traced fromgrounded battery, lower right hand winding of repeating coil 62, lowernormal contacts a?) of ringing key 63, center or ring members of plug 73and ack 330, relay 331 and thence to ground through the upper normalcontacts of jack 332. at the opposite end of the trunk circuit.

The response of relay 331 completes a circuit from grounded battery overresistance 333, signal 334, contacts of relay 331 to ground through thelower normal contacts of jack Plug 73 in jack 330 effects separation ofthe normal contacts of the jack and by closure of the lower contacts,current from grounded battery traverses a resistance 339, signal 338 andthence over the local or sleeve members of jack 330 and plug 73 toground. At this time signal 338 serves as a guard or supervisory signal.

In response to this call, a plug 335 of the cord circuit C3 may beinserted into jack 332. This effects separation of the normal contactsof jack 332 and closure ofthe lower alternate'contacts, therebyconnecting a resistance unit 336 in parallel with and shunting signal334. Ground over the sleeve members of the jack 332 and plug 335 beingprovided by the cord circuit, in substitution of the ground at the lowernormal contacts of jack 332.

Since the cord circuit C3 is a duplicate of the cord circuit C, currentwill be supplied from grounded battery of cord C-3 over the center orring conductors of the plug 335 and jack 332 to the winding of relay337, the upper or tip members of jack 330 and plug 73 through the upperrighthand winding of repeating coil 62 to ground. The correspondinggrounded battery, present in the cord C, will cause current to traverserelay 331 to ground through the repeating coil of the cord 03 tomaintain relay 331 energized. Resistance 340 will now be connected bythe forward contacts of jack 330 and contacts of relay 337 to groundover the sleeve members of the connection to the cord C, therebyextinguishing signal In establishing the operators telephone set withthe two-wire cord circuit C, key 65 will be operated. The upper contactscf of this key provide a ground connection for the circuit through relay28 to grounded battery, thereby effecting response of the relay 28. Acircuit is established which may be traced as follows from the uppermain conductor 66 of the cord C by way of the second upper forwardcontacts 0d of key 65, left hand winding of repeating coil 68, condenser69 and lower forward contacts (lb of key 65 to the opposite conductor 67of the cord.

-When the relay 28 operates, a circuit is established which may betraced as follows. From ground over the primary winding of repeatingcoil 68, lower alternate contacts of relay 28, transmitter 31 andretardation coil 9 to grounded battery, while another circuit extends inhalf tap relation from the upper terminal of the secondary winding ofinduction coil 68 by way of the upper alternate contacts of relay 28,receiver 23 and next upper alternate contacts of relay 28 to anintermediate half tap oint on the secondary winding of induction coil68. The separated contactsv of relay 28'disconnect the transformer 33and also induction coil 29 employed for four-wire working, as alreadydescribed. For the circuits just traced, the forward contacts of relay28 connect transmitter 22 and receiver 23 to operate by way of inductioncoil 68 in twowire relation to the circuits of the cord circuit C.

'lhe gnal at either end of the trunk circuit may be flashed by theremoval and fit) till

re-insertion of the plug at the opposite end of the trunk, while"removal of a plug Will cause the signals at each end of; the circuit tobe energized. To render this clear, remoral of plug 73 from thejack 330effects the release of relay 33L, thereby disconnecting the shuntingresistance 336 to permit the illun'iination oi signal 33 l by current-from grounded battery througl'i; resistance 333, signal 334, sleeveine'n'ibers of jack 332 and plug to ground on the cord circuit C3. Incase the plug 73 isnow re-inserted in jack 330, re-operatiionoi relay331 will re-apply resistance unit 336 in parallel with the circuit justtraced tor the signal 334, thereby of relay 381 removes the shunt patharound causing this signal to be extinguished.

' From the description ust given, it will be apparent that a singlerelay having a single forward contact,as the relay 331,1n

association with jack and cord circuit C 3 will serve either asa line orsupervisory signal control relay in the handling of telephone trafficover the trunk circuit 325. in a reciprocal manner, a correspondingrelay 337 may serve as a line or supervisory signal control relay forcalls originating at jack330. i i Assume now that a call has originatedat a station such as 378 on tandem circuit 327. In initiating thecall,removal of the receiver from its switchhook at station 378 completes acircuit which may be traced 'i rom grounded battery 725 over resistanceunit 379, first lower normal contacts of jack 380, relay 381, firstlower normal contacts of jack. 38:2, thence through the instrumentstation 378, through relay 383, upper nor-. nial contacts of jack 382,marginal relay 38a, upper normal contacts of jack 380. and resistanceunit 385 to ground.

transmittim station lu 73 of cord circuit C will be inserted into jack380. The lower group of contacts otjaclr 380 effect disconnect on ofgrounded battery through the winding of relay 201 (Fig. 2) and establisha shunt on signal 386 as already described for the call over trunkcircuit 325. Separationot .the first lower normal contacts of jack 380opens the circuit over which current is supplied through resistanceunits 379 and 385, current and ground being. new

substituted by way of repeatingcoil 62 0f' Due to the presence oiresistances 379 and 385 in the the cord circuit to the main conductorsof station 378, the marginal relay 384 will resp ond. The contacts,of'this relay establish a shunt path around relay 383 which will nowrelease and disconnect signal 387. hen the receiver is restored to itsswitchhook at station 378, cessation of current through the mainconductors of the line will etl'ect releaseot" relays 384: and 381;Release 23, to effect display ofthe signal which at this time is adisconnect indication. Assuming now that the call received from station378 is to be answered at the switch board of the radio receivingstation, lamps 386 and 387 will be lightedfas explained above and thecall willbe answered by inserting plug 335 01": the cord circuit C3 intojack 382. The upper and first upper normal contacts of this jack nowdisconnect the cir-V cuit fromthe distant jack 380, thereby etfectingthe release of relay 381 to extinguish signal 386 atcthe latter point,while battery over the ring conductorfot' the cord circuit C3 willtraverse the circuit, through the instrumentat station 378, returningthroughrelay 383 over the tip members of the'connection to ground on therepeating coil of cord C3. Circuitchanges, due to the presence of plug335 in jack 382 and the operated position ot'relay 383, serve to shuntthe lamp 387. On disconnection at station 378, relay 383 will bereleased, thereby effecting removal'ot the shunt path and permittingsignal 387 to be displayed. 7

Let it now be assumed that an operator at'OT .(Fig. 1) desires to callstation 388 of line 326. Plug 73 will be inserted'into jack 389 therebydisconnecting roundrand battery from the main conductors of this linedue, to, separation of the normal cont acts of the jack. A signal 390will be lighted at this time by current from the grounded batterythrough theassociated resistance unit, signal 390 and sleeve .mem-

bers of the plug and jackto ground on the cord circuitC. Operation ofringing key 63 and hand generator 2%, serve to apply ringing currentover conductor 50,lower alternate contacts of 'key 63, ring members atstation 388, flow of direct current through the repeating coil. of thecord circuit will effect the response of relay 391 to eiiect shunting ofsignal. 390. Under flashing or disconnect operations as station 388,relay 391 will be alternately energized and deenergized to respectivelydisplay or extinguish the signal 390 in a manner similar to that alreadydescribed for flashing and disconnect operations in the trunk circuit385.

When desired, the jack 61 of the line L may be employed for so-calledpatching of this line to come primarily under the control of theswitching equipment at the distant radio station, or this line may bepatched directly to the circuits 325327 for service therewith. Apatching cord, not shown, but well known in the art, may be associatedwith jack 61 of the toll line and with jack 315 of the trunk circuit318. In turn, a second patching cord may be associ ated from jack 317 tothe jack adjacent the plug 321 thereby providing that the line L mayterminate at the duplicate equipment 'I1 at the radio receiving station.This prepares circuits so that the four-wire cord circuit C2 may beemployed for establishing connections between the land line L and theradio transmitting and receiving equipment in the manner alreadydescribed for connections established at the other switchboard. Similarcombinations relative to parallel, series or tandem or combinations ofparallel and series connections may be carried out relative to the twoswitchboards in a similar but inverse manner to the arrangements alreadydescribed.

In connection with the radio transmitting system, a coil 392 may bepositioned adjacent the electromagnetic equipmentof the trans mittingcircuits, or of an inductive turn, as shown in the antenna lead. Asshown, the coil 392 may connect to suitable amplifierrectilier equipment393 for causing the relay 394 to respond during the periods that energyis supplied to the antenna. This results in the application of currentfrom grounded battery over an obvious circuit through rela'ys 395 and306 to energize the respective signals 397 and 398 at the two switchingpoints. The display of these nals indicates to operators at therespective stations that the radio transmitting system is energized foruse.

call signal, incoming over the radio side. may comprise two alternatingcurrents of diiierent frequencies as modulations of the carrier wave.Upon detection or the incoming wave by the radio receiving equipment, animpulse of current comprising the two different frequency currents willbecome effective to cause two correspondingly tuned relays 399 and399-2; to respond.

eaters Simultaneous separation of the normally closed contacts of theserelays releases relay 701 which is normally energized over an obviouscircuit. Relay 701 in releasing applies current from grounded batterythrough relay 702, relay 703, normal contacts of jack 310, relay 704 toground through the normal contacts of jack 303. Response of relays 703and 704 apply grounded battery through obvious paths to respectivelyenergize signals 705 and 706.

The call. may be answered at either switching equipment and, assumingthat response is made at the first switchboard, insertion of plug 207 ofthe cord G1 into the jack 303 effects the separation of the normalcontacts of this jack to disconnect the-circuit through relays 702, 703and 704. However, these relays were held energized, following theresponse of the relay 702, by current from a grounded battery connectedover the alternate contacts ofthe relay 702. This battery having beenthereby substituted for the battery initially connected over thecontacts of relay 701. hen the plug 207 is fully seated in jack 303, acircuit will be prepared from ground through relay 201, upper normalcontactsot key 220, upper sleeve members of plug 207 and jack 303,thence over the now closed alternating contacts of jack 303 to thecircuit'already traced through relays 704, 703 and 702. Therefore,during the period of a connection, a subsequent call signal will effectthe response of the relays 399 and 399A to cause the re-operation of therelays 702, 703 and 704 to display signals 705 and 700 as alreadydescribed. 0

In responding to such asignal, operation of the talking key formed ofunits 220-221 disconnects the circuit to ground through relay 201 at theupper normal contacts of the key 220. effecting release oi relays 702,703 and 704 thereby restoring the signals 705 and 706 to normal, ornon-operated position.

For call signaling. over the radio link, the plug 208 is inserted injack 305, key 215210 of cord circuit C1 is now operated, followed by theoperation of a master signaling key 245. Current from sources 240 and247 willflow over the main conductors of: the plug 208, jack 305, to the'adio transmitting equipments TR and a carrier wave modulated by thecurrent from the sources 240 and 247 will be supplied to and radiatedfrol'l'i the antenna 302.

At a distant point, such as at a station equipped as shown in Fig. 4,the called signal modulated wave will be received by an antenna 400,detected by the receiving equip ment 401, and the detected currents willbe supplied to the two correspondingly tuned alternating current relays402 and 403. Simultaneous operation of these relays opens the connectionto ground of a circuit including the relay 404 which is normallyenergized over an obvious circuit. On release, the latter relayconnect-s grounded battery to a circuit through relay 4.05, resistance406 and thenormal contacts of jack 408 to ground. \Vh'en the relay Lresponds, its contacts connect a second grounded battery, insubstitution of the first mentioned battery over the contacts of relay ato reta n relay 405 energized and also to supply current through signal407 and thenormal contacts of the trek 408 to ground.

For telegraph operation. ke 271 of the equipment 'S-1 (Fig. 2) may bemomentarily operated. thereby applying current from grounded batterythrough relays 235 and 232 to ground. In responding, separation of theupper contacts of relay 235 disconnects a normally closed path in shunt'to the output Winding of transformer 2&8. On closure of the lowercontacts of relay 235, grounded battery is applied through normalcontacts of key 2&9, signal 250 and relays 235 and 22 to retain theserelays energized. The contacts of relay connect the secondary Winding ofthe transformer 251 to energize the cathode or filament 252 of athree-element vacuum tube 253; the primary Winding of this transformerbeing energized from a source From an intermediate half-tap pointconnecting units 255 and 256 connected in series to form a bridge acrossthe filament 252,' a circuit may be traced through B battery257,'retardation coi'l258, theprhnary Winding of an output transformer25!.) to the plate element 2600f the tube 253. The coudensersshown'connected from the retardation coil to points of the plate circuitserve to establish a. condition of resonance relative to a certainfrequency, which in the present case may be assumed as one thousandcy-cles per second.

Upon. closure of key 261, grounded battery isconnectedthrough relay 263,retardation coil 262, key 261to ground. The re sponse of relay 263closes a circuit which may be traced from the filament by Way ofresistances 255 and 256, through the secondary Winding of transformer25S) and contacts of relay 263 to the grid element 26;: of tube 253. Thelatter circuit forms a socalled feed back to produce and maintain theproduction of oscillations in the tube circuit. These oscillations aresupplied to transformer 248 by Way of an intermediate transformer 265.

Assuming now that the plug 208 is present in jack 305 with the talkingkey units 220-221 in their operated positions, alternating current ofone thousand cycles per second Will be supplied from ground through theright hand Winding of transformer'248, conductor 30, the primary Wind-205 and 206.

to the antenna 302.

. ployed for talking,

31 to ground through the condenser 60. I

As already described, the operated position of key. 221 connects thesecondary Winding of induction coil 29' and with "conductors Ittherefore iollows that each closure of the telegraph key'26l will result inan impulse of alternating current, which traverses the connection overtheplug 208 and jack 305, to the radio transmitting equipment RT fromwhich it will be supplied as a modulation of the carrier wave The righthand Winding of transformer 248 is of low ohmic or direct currentresisance theretore,'it is substantially innnaterial Wlretherthis Winding isin series With the battery supplyottransmitter' 31, as already.v tracedthrough the Winding of induction coil 29. Accordingly, during theperiods "when relays .235 and are energized as indicated by'the displayof signal. 250, the operator may either talk or telegraph over the radiotransn'iitter; i. -e.,'during periods when the telegraph key 26l is-atrest the transmitter 31 may be em- 4.- Y 1 telegi aphm bnnilar equipmentat a distant radio station may be operated for telegraph signah ling,the signals being ,received by Way of the antenna 801 and radioreceiving equipment RR; Atter detection in the receiver RR the signalimpulses will be transmitted ceiver 23 forreception of suchineon'iingtelegraphic signals. Without other manipulation on the part of theoperator. A key 76 may be operated it desired to apply ground to thetransmitter circuit and there by 'shunt the transmitter 31 for thealternating telegraph signal currents. This key mayalsobe employed as atransn'litter cutoutkey at any time in the handling of telephonetrattid,I i 1 i The systen'roi direct current telegraph, employed with thepresent system Will now be described. A pole changer or telegraph key707 line relay 708, and a vibrator sounder 709. controlled by the linerelay and energized from an alternating current source 710 by Way'oi atransformer 7ll, may

While upon cessation of, talking the key 261 may be operated for Hillits,

form one station on. a line conductor 712; while a, similar key 266,line relay 267 and. sounder 268 1nay be present at asecond sta- "267 torespond to respectively operate the sounders 709 and 268 when signalsare transmitted from the right hand to the left hand station. In areciprocal manner, operation of the key 266 serves to transmit signalsfrom the left hand to the right hand station. The sounder 268 issupplied with energy from the alternating current source 275 by way of atransformer 276, which also supplies energy for the sounder 277.

WVhen desired the Morse line 712 may be connected to control the systemfor transmitting telegraph signals over the radio channel. This may beeffected by operation of key 269. Assuming the latter key is in itsoperated position and sending under way from key 707, each closure ofthe contacts of the line relay 267 establishes a circuit from ground byway of key 269, retardation coil 262 and the winding of relay 263 togrounded battery, causing the latter relay to respond and control thefeed-back circuit of the oscillator 253 in the same mannor as thatalready described for controlling it from the telegraph key 261.Further, assuming that plug 208 is present in. jack 305, direct currentsignals from the Morse line 712 will be translated into alternatingcurrent impulses at 1000 cycles per second which will be supplied by wayof the transformer .248, induction coil 29, talking key 221 and theconnection previously described to the radio transmitting apparatus andantenna 302.

The arrangement whereby busy test operations may be carried out by meansof the cord circuit C may be described by assuming that the talking key65 of this cord is in its operated position. Relay 28 will now ope atedue to grounded battery through the relay to ground through the upperforward contacts of the key 65 as already described in transferring theoperators receiver and transmitter 31, respectively, from thetransformer 33 and induction coil 29, to con trol through the inductioncoil 68.

Assume now that the upper or tip me1nber of plug 72 is applied to thesleeve of the jack 33-0 in performing a busy test operation. Currentfrom grounded battery, through the resistance 339 and signal 338 to theshell or sleeve member of the ack 330, will traverse the tip strand ofthe cord circuit as connected by way of the upper normal contacts of theringing key 71 to ground through the upper left hand winding ofrepeating coil 62. This current effects a change of poten' tial levelhetwccnthe main conductors (it; and 67 of the cord circuit, whichbecomes effective through the condenser (39 and the secondary winding ofthe repeating coil 68 to cause a click in the telephone receiver 23. Inthe present instance this click may be taken as an indication that theline 825 is idle.

In the event that a cord, similar to the cord circuit C, is connected toa jack associated. with. the jack 330 on the line 325,

ground potential from the sleeve conductor of such. cord circuit to theshell of the jack, will prevent How of current from grounded battery, asdescribed when the tip of the plug 7 2 is inserted into jack 330. Insuch a case, absence of a click in the telephone re-. cci'ver is anindication that the line 325 is busy.

l Vhere it may be desirable, the order of the busy test indications maybe reversed, that is, for an idlecondition of a circuit no click will bepresent, while for a busy line, a click will be heard in the operatorstelephone receiver when the tip of a plug is touched to the shell of ajack on a line or trunk which is busy. This may be done by reversingbattery and ground for the sleeve or local circuit of a cord and jack.For example, on the trunk 825 the resistance 339 may be connected toground instead of to a battery, while the sleeve strand of the cord Cmay be connected to battery instead of to ground. Again the winding ofthe auxiliary signal relay 201 may be connected to battery instead ofbeing grounded, as shown.

The equipment for a ship or similar station (F 4) may comprise anantenna 4.00 connected to a receiving equipment 401 and also to atransmitting equipment 411. In establishing connection of a telephoneset to the radio transmitting and receiving apap aratuses a cord 4-12 isused to connect jacks 413 and 414, and similarly a cord 415 is used toconnect conductors 408 and 416. Over the main jacks of the respectivecords and the main contacts of the jacks, with which they areassociated, the output and input windings of transformers 417 and 418will be respectively connected to the radio transmitting and radioreceiving equipments. To connect an operators telephone equipment GT2,comprising a transmitter 419 and re ceiver 420, with the radio equipmenta talk ing key, formed of units 421 and 422, is operated.

For the transmitter a circuit may now be traced from the upper terminalof the right hand or primary winding of the transformer 41?, lowernormal contacts be of a key 423, upper normal contacts gh of this key,lower normal contacts 72d of key 424, conductor 46h, upper normalcontacts jh of key 425, lower. forward contacts at of the key 4-21, thesecondary winding of induction coil 426, upper forward contacts 0/ ofkey 421, upper normal contacts 7'Jy' of the key 4 5, conductor465,11pper normal contacts eg of the key 424, the upper normal contactsM of the key 423, the lower normal contacls ft: of this key to the lowerterminal of. the primary winding of transformer 417.

For the receiver a circuit may be traced from the upper terminal of thesecondary winding of the transformer 418 over the upper normal contactskg of key 427, lower lllll normal contacts 06 of this key, upper normalcontacts fe of key 428, lowernormal contacts fa of key 425, upperforward contacts er] of key 422, winding 429 of transformer 430, lowerforwardcontacts ha of key lower normal contacts of key 425, lower normalcontacts do of key 428, lower normal cont-acts cf of key 427,'the uppernormal contacts 770 of this key to the lower terminal of the secondarywinding of the transformer 418. y

Voice currents from the transmitter 419 will be suppllied through therepeating coil 426, over the circuits traced above, to the radiotransmitting equipment 411 and voice modulated carrier waves will besupplied to the antenna 400. Voice or signaling modulated carrier Wavesincident upon the an-.

tenna 400 will be supplied to and translated in the radio receivingequipment 401 to produce voice or signal currents which will be suppliedover the circuits traced above, including the transformer 430, to thereceiver 420.

Communication, by means of the ship equipment described above, may beeffected with anothership having a similar equipment, or communicationwith a land station similar to the station shown on Fig. 3, or

with stations including equipment similar to that shown in Fig. 5, to behereinafter described.

A. connection for a communication over the radio channel may be made todifferent telephone stations aboard ship. To llltlS-r trate how this maybe done, an extension of the connection to station TS will be traced.431 when operated complete a circuit which may be traced as follows.From the upper terminal1 of the secondary winding of mduction coil 432'at the station TS over the upper, forward contacts ml of key 410, uppernormal contacts of key 433, upper normal contacts 6g of the key 424,thence over the circuit already traced through the contacts ihj and feof'key 423 to the lower terminal of the primary winding of thetransformer 417. .The-connection from the lower termi-' nal of thesecondary winding of the induction. coil 432 extends over the lowerforward contacts 12a of key 410, lower normal contacts of key lowernormal. contact-s (Z?) through the key 424 thence to contacts lag and obofthe key 423 already traced to the upper terminal ofthe primary windingof the transformer 417.

From the right hand terminal of the telephone receiver 434 a pathextends, over the upper forward contacts. of key 431, upper forwardcontacts of the key 435, upper normal contacts, cf of the key 428,thence through contacts 710 and h of the key 427 already traced to theupper terminal of the secondary winding of the transformer 418.

A key formed of groups 410 and- From the lefthand terminal of receiver434 I a pathextends over the lower forward contacts of key 431, lowernormal contacts of key 4.35, lower normal contacts do of the key 428thence through contacts cf and of key 42? to'the lower terminal of the.secondary winding of the transformer 418. When the receiver 434 isremoved from the switchhook at thestation TS, the transmitter 436 willbe connected to such speech currents to the radio transmitter 411, fromi which a speech modulated carrier wave is supplied to the antenna 400,the receiver 434 will be connected to receive speech currents tov theradio receiver, which is connected to the antenna400.

l Vhen the receiver is replaced on the switchhook at the station TS,during a period of a communication, a circuit will be completed asfollows. From grounded battery through a signal device or lamp 437, theupper. normalcontacts fe of key 438, upper alternate contacts fg of key410, normal contacts439 under control of the switch-hook thence toground through an audible signal device 440. Signal .437 indicates tothe operator that disconnect has taken place at the station TS andtherefore, thekey 410 -431 may be restored to'normal.

Assuming that the circuit is in normal condition and a call is initiatedat the station TS. Removal of the receiver 434 from the switchhookestablishes a circuit from ground through a signal 440, contacts 441 ofthe switchhook mechanism, the upper normal contacts cf of key 410, theupper through signal-437 to grounded battery. Display of the signal 437serves as a, linesignal for this call, while the signal 440 may becontinuously energized until responseto the call has been made by theoperation of "normal contacts 6; of key 438, thence' key 410431. Whenthe circuits are in v normal condition already traced and receiver 434is replaced, the path for the lamp 437 will be transferred by the uppercontactsof the key 410 for control through the contacts 439 of theswitchhook mechanism, This again gives the disconnect signal and key41043l is returned to normal position. The equipment at the station T81is a duplicate of the equipment at the station TS and is under thecontrol of akey formed of units 442 and 443. The instrument atthisstation may be connected for service through the radio equipments.

Equipments represented by 444 and 445 may be used to insure secrecy ofthe communication over radio channels. Assuming that a station equippedas shown in Fig. 4 is in communication with another ship or stationsimilarly equipped, the devices 444 will operate to mutilate inapredetermined manner the voice or signaling currents. outgoing over thesending radiochannel At ated.

the distant vessel an equipment, corresponding with that at 445 willoperate to restore the signals or speech currents to their normalcondition of intelligibility before they are supplied to the receivingdevices.

The key formed of units 423 427 is used to connect or disconnect theequipments 444 and 445, for secrecy communications, be tween thetelephone set and the radio terminal apparatus. Assuming now that thesekeys are in their operated positions, a circuit will be provided fromthe upper terminal of the secondary winding of the trans former 417 overthe lower alternate contacts M of key 423 through the apparatus 444,upper alternate contacts 17c of key 423, the upper normal contacts ge ofthe key 424, thence to the conductor 465 which may lead to the operatorstransmitter 420 or to the transmitter of the stations TS or TSl, overthe circuits already traced. The lower terminal of this winding of thetransformer 417 is connected through the lower alternate,

contacts ed of key 423, equipment 444, upper alternate contacts z'h ofthe key 423, thence through the lower normal contacts lid of key 424 toconductor 466 which may be connected to either the transmitter 420 orthe station TS, T51.

For the equipment 445 a path extends from the upper terminal of thesecondary winding of transformer418 over the upper alternate contacts Mof key 427, equipment 445, lower alternate contacts (Z6 of key 427,lower normal contacts 0d of key 428 to the conductor 460, while thelower terminal of this transformer winding is connected over the upperalternate contacts M of key 427, the equipment 445, ab of key 427,thence through the upper normal contacts f6 of key 428 to the oppositeconductor 461, whereby either the opera tors receiver 420 or thereceivers of the stations TS, TSl may be connected thereto according tothe positions in which the various switches already described may havebeen placed.

A key 447 under control of the operator serves for establishingcommunication with the station TS2at which may be located the devices444, 445 of the secrecy system as well power and other equipments forthe radio system. In initiating a call from the station TS2 removal ofthe receiver from the switchhook at that point applies ground overcontacts of the switchhook mechanism, the normal contacts do of key 447,thence through signal 448 to grounded battery. In response to thissignal, the key 447 is operlt hen this is done the circuit of the signaldevice 448 will be switched to the now separated contacts 449 of theswitchhook mechanism where the circuit will stand open. A circuit maynow be traced from the upper terminal of the secondary winding loweralternate contacts ary winding of an induction coil 452, the

lower group of forward contacts at of key 447, resistance unit 453, thelower terminal of the secondary winding of the coil 426. A secondcircuit may be traced fromthe up per terminal of the winding 429 oftransformer 430, resistance 454, the lower contacts be of the key 447,thence through the induction coil 452, receiver 451, the upper contactsgh of key 447, resistance unit 455, to the lower terminal of the winding429 of the transforn'ier 430. With the circuits just traced thetransmitter 419 and receiver 420 of the operators equipment will beconnected for communication with the equipment at the station TS2. Whenthe receiver is restored to its switchhook at the latter point, groundis applied through the contacts 449.to supply current to the signal lamp448 which is lighted, thereby indicating a disconnect condition;whereupon the key 447 will be restored to its normal position.

A key 456 at the operators position and a signal 457 at station TS2serve as a means for calling from the first to the latter point.

In case it is desired to reverse the relation of the operatorstransmitter and receiver with respect to the outgoing and incoming radiochannels, a key 425 may be operated. In its operated position andassuming that the key formed of units 421-422 is in its operatedposition, a circuit for the transmitter may be traced as follows. Fromthe upper terminal of the secondary winding of the induction coil 426,upper forward contacts cf of the key 421, upper alternate contacts cl ofthe key 425, upper normal contacts cf of the key 428, thence throughnormalcontacts b0 and gh of the key 427 as already traced to the upperterminal of the right hand winding of transformer 418. From the lowerterminal of the secondary winding of the coil 426 the connection extendsover the lower forward contacts 5a of the key 421, the upper alternatecontacts M of the key 425, lower normal contacts do of the key 428,thence through normal contacts of and of key 427 to the lower terminalof the winding of the transformer 418. From the upper terminal of thewinding 429 of the transformer 430, a path extends through the upperforward contacts ad of key 422, lower alternate contacts cd of key 425,upper normal contacts cg of key 424, thence through normal contacts 707'and fa of the key 423 to the lower terminal of the right hand winding ofthe transformer 417. The lower terminal of the winding 429 of thetransformer 430 is connected over the lower forward contacts bar of key422, lower alternate contacts ba of key 425, lower normal contacts db ofkey 424, thence through noriao stands hereinafter.

mal contacts hg and-c?) of key 423 to the upper terminal of the windingof thetranstormer417 v In this position of the circuits it will be clearthat the; transmitter 419 connected to the lower channel through thetransformer 418 while the receiver 420 stands connected to the upperchannel through the. transformer 417.

For monitoring on the connection ust described, a key formed of units458459 is moved to its operated position. A path from conductor 461 ofthe speech circuit connected to theincoming radio channel may be tracedover the lower normal contacts fee of key425, upper alternate'contacts@(Z of key 459, winding 462 ofthe transformer 430, lower normal contactsof the key 422, winding 429 of the transformer 430, lower forwardcontacts ha of key 459, lower normal contacts to of key 425, to theopposite conductor 460 of the speech circuit associated with theincoming radiochannel. The windings 429 and 462 of the transformer 430are connected in series across the incoming radio channel to form abridge to which the receiver 420 is coupled for monitoring. Theincreased impedance due to addition of the winding 462 at this timeresults ina conditionot substantially zero loss as regardsthe incomingtransmission. I lVhen monitorii'ig on the circuit just described the key458 serves to disconnect a sidetone circuit, in a manner to be describedPAgain, operationof the reversing key 425 serves to transfer-thecircuits of the receiver 420 from the conductors 460 and 461 ofthe'incon'iin'g side of the radio chaunel to conductors i465 and 466which, as alreadyztraced, constitutes part of the speech circuitassociated with the outgoing radio channel, thereby permitting theoperator to n'ionitor'on'either the incoming or outgoing channel. v v vDuring periods when the operators telephone set is in the talkingposition, aside tone circuit from the transmitter 419 to the receiver420 is provided over a path from the upper 't-crn'iinal of thetransmitter 419 by way of a condenser 463, normal contacts of key 458,winding 462.01 the transformer 430' unaer normal contacts of the he 1 ll459, and resistance unit 464 to the lower terminal i of the transmitter.The wind.- ing 462 in this instance serves to supply re ceiver 420 witha predetern'iined amount of' voice current from the transmitter 419.During the monitoring period, as already described the winding-462 isdisconnected relative to the side tone circuitand connected with thewindii'ig 429 of the transformer'to 'fOIHI a high impedance bridge pathacross av speech circuit of the radio channel,

- Call signaling may be etl'ected by operating a key formed oi the units424428 and a 'key'467. Operation of these keys completes alternatecontacts by of the key: 424, thence through normal contacts .lcj and f6of the key 423 to the opposite terminal of thewindi'ng oi thetransformer 417. 470 and 471 represent alternating current sources,which for convenience may be similar to the oscillator system S1(Fig.2). The current supplied by sources 470 and 471 will be ofrespectively dillerent' frequencies and on arriving at a distantstat-ion, snmlar to the statlon shown in Mg. 3 or the station beingdescribed and illustrated. in Fig. 4, are used to energize.

two relays, corresponding with either relays 399 and 3994 or 402 and403, to control a signal device as already described in connection withthe signal receiving systen'i of Figs. 3 and 4. I i

hen the station TS is connected over four vire circuits to the radiotransmitting and receivingequipments, voice currents for side toneefi'ects may traverse a relatively high impei'lance circuit tormed vby acon: denser 483 and resistance unit 484 connected from the terminals ofthe transmitter-436 in bridge on the main leads of the receiver 434. Acorresponding resistance. and condenser nerve the same purpose forsidevtone, eltects when four ,wireis used to connect the. station TSltothe radio apparatuses. v A group connection between stations Tb, Tilland TS2may be had by operation of the keys formed of units 438, 446, 495and 496 and also 447'. hen these keys are operated, the instruments willall be connected common to the conductors4i'9 and 480 for so-calledconference communication. At such times the operators transn'iit'ters41-9 and 420 may also be included in such a connection over circuitsalready traced toeconductors479, 480, 485 and 486. v a

The radio-wire system shown in Fig. 5 may be used at a station which isadapted for communicating with other land lines for telephony, or may beused for. communication by radio with ship stations or other landstations'ot the type described above. A line circuit L4 is connectedthrough a jack 500, a. signaling key 501,,onepair1of terminals of theseries winding ota hyhrid COlltlZtIlSfOlll'lEl' 502, the other pair ofthe terminals of the series winding beingconnected to an artificial lineor network, 503

which electrically balances the line L4. The upper output winding-pfthe/hybrid coil 502. is connected through a splitting key 504 toconductors 505 and 506.1 The bridge points. of the hybrid coil ,502 are.connected i

